This is a competitive renewal of a project aimed at understanding regional differences in fatty acid metabolism. It is clear that there are regional differences in fat distribution, that ultimately must be due to regional differences in either lipolysis or fat uptake. However, which processes differ is not known. The P.I. has used the stable isotope tracers, delivered in meals, and combined with adipose biopsies to study fatty acid uptake and disposal. Using tracers, fat can be oxidized, stored in subcutaneous fat or unaccounted for. It is assumed that this fat is stored in visceral adipose tissue. The P.I. found that upper body subcutaneous fat took up more meal fatty acids than lower body subcutaneous fat, but that men and women did not differ in this process. It is thought by the P.I. that the isocaloric feeding involved in these studies may have masked gender differences and that perturbations in energy balance may also be required. Thus the P.I. proposes to study the effects of amount of dietary fat on the meal fatty acid disposal in non-obese men and women. The P.I. will also recruit patients scheduled for elective laparoscopy in order to determine if the unaccounted for tracer ends up in visceral fat. The hypothesis to be tested is that regional differences in body fat gain in response to overfeeding will be due to differences in regional differences in fatty acid uptake.